Yes, 'done' can have this meaning. But it's rare by itself. You'd more likely see, "A common-law marriage wasn't the done thing in the past"; "Common-law marriages just weren't done in the past.""A common-law marriage wasn't done in the past." Is it OK to say this to mean that a common-law marriage was not socially acceptable in the past?
That's a strange inference. I would say that, as evidenced above, it is correct.As is evidenced above, it's not.
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